"Web services" enable partners to exploit applications via the Internet. Individual services can be composed to build new and more complex ones with additional and more comprehensive functionality. In this paper, we apply the Web service paradigm to electronic learning, and show how to exchange and maintain learning objects is a corresponding e-Learning system. We start from a perception of core "e-Learning activities" as processes, which enables us to break central functionalities of an e-Learning system down into several stand-alone applications; these can then be accessed as Web services. However, building a decentralized system by composing suitably chosen Web services to achieve a functionality similar to that of a traditional e-Learning system leads to a variety of challenges, two of which are discussed in detail: (1) Storing learning content in a distributed fashion, and (2) dynamically exchanging content when necessary or appropriate. The paper also discusses some of the problems arising from storing data on different servers.